K. Verfondern - Safety Considerations on Liquid Hydrogen

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SAFETY CONSIDERATIONS ON
LIQUID HYDROGEN
(PART 2)
Karl Verfondern
Research Center Jülich, Germany
2nd European Summer School on Hydrogen Safety
Belfast, July 30 – August 8, 2007
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Types of Cryogen Release
- Catastrophic failure
from high internal pressure
- Release of a jet stream of
liquid or gas or two-phase
mixture from pressurized
system
- Release of liquid forming
pool on the ground
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Cryogenic Pool Phenomena
150 l of LN2 spilled on water
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Vaporization of a Cryogen
Film boiling
Transition phase
Nucleate boiling
Heat flux density
vs. temperature
Heat sources
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Nukiyama Curve of Heat Flux Density
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Vaporization Tests with LN2
Isolated bodies of
- bitumen
(road surface)
- concrete wet / dry
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Vaporization of 1.5 l of LN2
Mass loss
dry concrete
wet concrete
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Vaporization of 1.5 l of LN2
Temperatures in depth
dry concrete
wet concrete
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LH2 Pool Regression
Body:
paraffin wax
in 65 mm dewar
Zabetakis 1960
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Vaporization Behavior of LH2
Release of 3 l of LH2
No wind
Zabetakis 1960
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Cryogen Pool Spreading
Strongly depending on
- release mode
(instantaneous / continuous
- type of ground
(solid / liquid)
Release on water
Brandeis 1983
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Cryogenic Pool Behavior (1)
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Cryogenic Pool Behavior (2)
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Cryogenic Pool Behavior (3)
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Cryogenic Pool Behavior (4)
Pool Profile
continuous release
instantaneous release
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LN2 Spill Tests on Water (KIWI) at FZJ
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LN2 Pool Shape and Ice Formation
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WE-NET LH2 Spill Tests (1993 + 2000)
Chitose 2002
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Cryogenic Pool Burning
Overpressure
Flame geometry
Zabetakis 1960
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Cryogenic Pool Burning
Regression depending on pool diameter:
D < 0.2 m: heat transport by conduction dominant
D > 0.2 m: heat transport by radiation dominant
Brabauskas 1983
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Computer Model LAUV
• Simulation of radial spreading of a cryogenic liquid
on the basis of the shallow-layer differential equations;
• Instantaneous and continuous release on solid, humid,
or liquid ground;
• Heat conduction equation applied, if ground is solid;
• Ice formation, if ground is water;
• Atmospheric convection and insolation neglected;
• Validation against
LN2 and LH2 spill tests
and LNG spill test data from literature.
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Shallow-Layer Equations
1. Conservation of mass
∂ (r h) ∂ (u r h)
+
+ r (v − w) = 0
∂t
∂r
v – vaporization rate, w – source rate, m/s
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Shallow-Layer Equations
2. Conservation of momentum
 F
∂  u2
∂u

+
+ δ g h  +
= 0
∂t
∂r  2
 h
δ
– reduction factor, F – friction force
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LAUV Postcalculation of LNG Spill
2.5 m3 of LNG
in 300 s
at varying rate
dry concrete
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NASA LH2 Spill Tests (1980)
9.2 m dia spill pond
Courtesy Jose Chirivella, Ergo-Tech Systems Inc.
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LAUV Postcalculation of NASA Test #6
5.1 m3 of LH2
in 38 s
compact sand
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BAM LH2 Spill Tests in Cottbus (1994)
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LH2 Spill Test Arrangement
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LH2 Spill Test on Water
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LAUV Postcalculation – LH2 Spill on Water
5 l of LH2
in 62 s
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LAUV Postcalculation – LH2 Spill on Al Plate
6 l of LH2
in 62 s
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Prediction LH2 Release from CRYOPLANE Tank
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Comparison of Different Cryogens (1)
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Comparison of Different Cryogens (2)
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Conclusions
• Phenomena of cryogen pool spreading and
vaporization are principally understood.
• Modeling efforts have led to simplified, but
appropriate simulation of phenomena.
• Experimental data basis for LH2 is still very
poor and needs further extension.
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Thank you
for your kind attention !
email: [email protected]